PALEOZOIC ROCKS AND ERA. 



30? 



FIG. 234. Dactylothe- 

 ca dentata. (After 

 Zeiler.) a, spore case 

 enlarged. 



possess a high interest on that account. 

 We shall treat of them under three 

 heads, viz.,, Lepidodendrids, Sigilla- 

 rids, and Calamites. 



1. Lepidodeiidrids. Every part of 

 these has been found roots, stems, 

 branches clothed with leaves and tipped 

 with fruit. They may be restored, 

 therefore, with some degree of confi- 

 dence. Imagine, then, a trunk two, 

 three, or even four feet in diameter at 

 its base where it joins the wide-spread- 

 ing roots ; marked with regular rhomboidal figures, which 

 are the leaf -scars (Fig. 236) ; branching widely, but not 



profusely ; the great branches, 

 clothed with scale-like or needle- 

 like leaves, stretching aloft, like 

 uplifted hairy arms, to the 

 height of fifty or sixty feet, and 

 terminating in scaly cones like 

 club-mosses. The most common 

 findings are flattened stems with 

 beautiful rhomboidal markings 

 (Fig. 236), looking much like 

 rhomboidal scales of a ganoid 

 fish ; hence the name Lepido- 

 dendron, or scale-tree. 



There can be no doubt that 

 the Lepidodendron was a lyco- 

 pod, or club-moss ; but its inter- 

 nal structure, as well as its great 

 size (club-mosses are now but a 

 few inches, or, at most, a few 

 feet high), ally it strongly with 

 conifers. We may regard it, therefore, as a lycopod, with 

 characters connecting it with conifers. 



FIG. 235. Restoration of a Lepi 

 dodendron. (By Dawson.) 



